Sunday, November 08, 2009

The HoverBot CAn Electrically Powered Flying RobotSUMMARYThis paper describes the development of a fully autonomous or semi-autonomoushovering platform, capable of vertical lift-off and landing without a launcher, and capable ofstationary hovering at one location. The idea to build such a model-sized aerial robot is not new; several other research institutes have been working on aerial robots based on commercially available, gasoline powered radio-control model helicopters. However, the aerial robot proposed here, called the HoverBot, has two distinguishing features: The HoverBot uses four rotor heads and four electric motors, making it whisper-quiet, easy-to-deploy, and even suitable for indoor applications. Special applications for the proposed HoverBot are inspection and surveillance tasks in nuclear power plants and waste storage facilities.

Without a skilled human pilot at the controls, the foremost problems in realizing a model helicopter-sized flying robot are stability and control. It is necessary to investigate the stability and control problems, define solutions to overcome these problems, and builde a prototype vehicle to demonstrate the feasibility of the solutions. The proposed HoverBot will have eight input sensors for stability and control, and eight output actuators (4 motors and 4 servos for rotor pitch control). The resulting control system is a very complex, highly non-linear Multiple-Input Multiple-Output (MIMO) system, in which practically all input signals affect all output signals. A surprisingly simple experimental control method, called additive control, is proposed to control the system. This method was successfully used in the current experimental prototype of the HoverBot (although with fewer input signals). It is also proposed to investigate two alternative control methods, adaptive control and neural networks, both of which appear to be especially suitable for the Multiple-Input Multiple-Output control problem.If successful, the project will result not only in a working prototype of a flying robot, butit will also provide important insight into the functioning of various control methods for verycomplex MIMO systems.

Control of the HoverBotThe control system of the HoverBot is designed to allow either fully autonomous operation or remote operation by an unskilled operator. To either, the HoverBot will appear as anomnidirectional vehicle with 4 degrees of freedom: (1) up/down (2) sideways, (3) forward/backward, and (4) horizontal rotation.

Creation of a Learning, Flying Robot by Means of EvolutionAbstractWe demonstrate the first instance of a realon-line robot learning to develop feasibleflying (flapping) behavior, using evolution.Here we present the experiments and resultsof the first use of evolutionary methods fora flying robot. With nature's own method,evolution, we address the highly non-linearfluid dynamics of flying. The flying robot isconstrained in a test bench where timing andmovement of wing flapping is evolved to givemaximal lifting force. The robot is assembledwith standard o®-the-shelf R/C servomotorsas actuators. The implementation is a conventional steady-state linear evolutionary algorithm.

ROBOTFive servomotors are used for the robot. They arearranged in such a way that each of the two wings hasthree degrees of freedom. One servo controls the twowings forward/backward motion. Two servos controlup/down motion and two small servos control the twistof the wings. The robot can slide vertically on two steelrods. The wings are made of balsa wood and solar,which is a thin, light air proof ¯lm used for modelaircrafts, to keep them lightweight. They are as largeas the servos can handle, 900 mm.

http://fy.chalmers.se/~wolff/AWNGecco2002.pdf

Energy-efficient Autonomous Four-rotor Flying RobotControlled at 1 kHzAbstract—We describe an efficient, reliable, and robust fourrotorflying platform for indoor and outdoor navigation. Currently,similar platforms are controlled at low frequencies dueto hardware and software limitations. This causes uncertaintyin position control and instable behavior during fast maneuvers.Our flying platform offers a 1 kHz control frequency andmotor update rate, in combination with powerful brushlessDC motors in a light-weight package. Following a minimalisticdesign approach this system is based on a small number of lowcostcomponents. Its robust performance is achieved by usingsimple but reliable highly optimized algorithms. The robot issmall, light, and can carry payloads of up to 350g.

THE FOUR-ROTOR HARDWAREA. General designOur flying robot has a classical four rotor design withtwo counter rotating pairs of propellers arranged in a squareand connected to the cross of the diagonals. The controllerboard, including the sensors, is mounted in the middle of thecross together with the battery. The brushless controllers aremounted on top of the booms. Figure I shows a photographof the flying robot. The weight without battery is 219g. Theflight time depends on the payload and the battery. Witha 3 cell 1800mAh LiPo battery and no payload the flighttime is 30 minutes. We measured the thrust with a fullycharged 3 cell LiPo (12.6V) at 330g per motor. With fourmotors the maximum available thrust is 1320g. Since thecontrollers need a certain margin to stabilize the robot alsoin extreme situations, not all the available thrust can be usedfor carrying payload. In addition, efficiency drops and asa consequence flight time decreases rapidly with a payloadmuch larger than 350g. Because of this we rate our robot fora maximum payload of 350g.

With a 350g payload, a flight time of up to twelve minutescan be achieved. The maximum diameter of the robot withoutthe propellers is 36.5cm. The propellers have a diameter of19.8cm each. The sensors used to stabilize the robot are verysmall and robust piezo gyros ENC-03R from Murata [14].The second design iteration of this robot is already functionalbut not fully tested and characterized experimentally. Thissecond version additionally has a three axial accelerometerand relies on datafusion algorithms, still running at 1kHz,to obtain absolute angles in pitch and roll.

The ROBUR project: towards an autonomousflapping-wing animatAbstractFlapping-wing flight is not applicable to huge aircrafts, but has a great potential for micro UAVs - as demonstrated by real birds, bats or flying insects. The ROBUR project aims at designing a robotic platform that will serve to better understand the design constraints that this flying mode entails, and to assess its capacity to foster autonomy and adaptation. The article describes the major components of the project, the tools that it will call upon, and its current state of achievement.Research on flapping flight maneuverabilityA generic model of a flapping wing aircraft has been designed, in which lifting surfaces aremodelled by a set of articulated panels (figure 2). In a first stage, this model will be used todesign a simple periodic controller for such a platform by using evolutionary algorithms (figure3). This controller is expected to generate a periodic, horizontal, flapping flight at a constantspeed.

Physical model used in this project.

http://animatlab.lip6.fr/papers/Doncieux_JMD2004.pdf

Quad-Rotor Flying Robot

New German UAV – microdroneA high technology very small UAV made in germany by microdrone GmbH. Can reach an altitude of 400m and stay in the sky for 30 minutes